Tuesday 26 June 2012 01.48 EDT
First published on Tuesday 26 June 2012 01.48 EDT

Militants have crossed into Pakistan from Afghanistan and killed 13 troops, beheading seven of them, according to the Pakistani military.

Officials said militants from Afghanistan had crossed into the north-western Upper Dir region on Sunday night and clashed with Pakistani forces on a patrol. Six Pakistani troops are said to have been killed immediately. Seven who went missing were beheaded, while four have not been found. The military's statement also said Pakistani troops had killed 14 of the militants.

Pakistan's new prime minister, Raja Pervaiz Ashraf, said he would complain directly to the Afghan president, Hamid Karzai. "We have strongly protested and I will, too, God willing, talk about this to Karzai," said Ashraf, speaking in Karachi.

The Pakistani Taliban say their fighters carried out the raid, but their statement did not say whether the attackers had crossed over from Afghanistan. They said Pakistani claims of militant casualties were false.

The border skirmish is a new sign of tensions between the uneasy neighbours. Pakistan has complained that militants use parts of Afghanistan for sanctuary to stage attacks inside Pakistan. That claim helps Islamabad counter frequent US and Nato complaints that militants behind much of the violence in Afghanistan come from Pakistan.

The deputy border police commander for eastern Afghanistan, Major Mohammad Ayub Hassainkhail, said the Pakistani military had informed police on Monday that one of their patrols was missing. He denied the militants had crossed from Afghanistan, saying: "They have plenty of militants on their side. Why would the militants cross over from Afghanistan? I strongly reject this claim."